1. Field of the Invention
This invention generally relates to nuclear magnetic resonance (NMR) pulse sequences useful in the evaluation of earth formations. More particularly, the invention relates to NMR pulse sequences which may be used by a nuclear magnetic resonance logging tool for measuring earth formation properties such as porosity, permeability, and irreducible water saturation.
2. Prior Art
Nuclear magnetic logging tools such as disclosed in parent patent application SN 06/901,084, measure the number and nuclear magnetic relaxation rates of hydrogen atoms in the pore space of rocks by measuring the amplitude and decay rate of signals resulting from pulse sequences. In essence, the nuclear magnetic logging tools send a stream of pulses into the formation and monitor the returning pulses. The measurements made are typically cyclical, with each cycle taking several seconds. Interpretation algorithms are then used to find the formation properties of interest.